The effect of absence or presence of supplemental heat for nursing piglets (a 250-watt lamp suspended 45 cm above the sleeping area for each litter) was studied from October to April in each of three successive winter seasons. Ambient room temperature was 21 C. Sows were fed a fortified corn-soybean meal diet and piglets did not have access to creep feed. Floors were constructed of either wood and expanded metal or steel slats and expanded metal combinations. In Exp. 1, piglets were given either no supplemental heat or a heat lamp from birth to 21 days. Percentages of piglets that died within the first 3 days were 13.4 and 4.4%, respectively. Total losses for the 21-day period were 18.5 and 11.0%, respectively. Average body weight gains were 3.50 kg for the unsupplemented piglets and 3.69 kg for the heat-supplemented piglets. In Exp. 2, 133 litters were used to evaluate the effects of the absence or presence of supplemental heat from day 3 postpartum. Supplemental heat was provided either from day 3 to day 6 or from day 3 to day 21. The control litters had no supplemental heat from day 3 to day 21. Neither sow feed consumption nor body weight change was significantly affected by treatment. Percentage death loss was not significantly affected by treatment, but piglet body weight gain was greater (p less than .01) when the heat lamp was used, for the total period.